Abstract
AbstractCurrent high strain rate testing techniques typically rely on the split‐Hopkinson bar (SHB). The early response in an SHB test is corrupted by inertia making it difficult to accurately characterise the transition from elasticity to plasticity for metals. Therefore, a new test method is required. This article is the second in a two‐part series which aims at developing a new high strain rate test for elasto‐plasticity identification using the image‐based inertial impact (IBII) method. The goal of this article is to validate the new method experimentally using IBII tests on aluminium 6082‐T6 (minimal rate sensitivity) and stainless steel 316L (rate sensitive). Comparison of the quasi‐static and dynamic stress–strain curves for the aluminium case showed minimal difference providing experimental validation of the method. The same comparison for the steel showed that the method was able to detect rate sensitivity.
Highlights
There are many scenarios in industry which subject metals to high strain rate loads for example: machining, forming, blast, crash etc
The traditional split-Hopkinson bar (SHB) method relies on the test sample undergoing uni-axial deformation with the sample in a state of quasi-static equilibrium [1, 2]
The results of numerical analysis and experimental validation presented in this study have shown that the ImageBased Inertial Impact (IBII) methodology can be used for the identification of elasto-plastic behaviour under high strain rate loading
Summary
There are many scenarios in industry which subject metals to high strain rate loads for example: machining, forming, blast, crash etc. In the early portion of an SHB test there are stress waves within the sample which violates the assumption of quasi-static equilibrium This makes it extremely difficult to accurately measure the elastic response of the material and for metals it is difficult to accurately characterise the transition between elasticity and plasticity. This leads to considerable scatter even in data for the high strain rate yield stress of common metal alloys. We observe that there is a large amount of scatter between different authors with the initial yield stress being anywhere between 325 M P a and 625 M P a This leads to considerable uncertainty about the overall strain rate sensitivity even when testing a material that is nominally the same steel alloy
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